Technical Note on Canvas for Extreme Cold

[MacEntyre]

I thought I would explain something that has become clear to me lately.

FourDog and others say, "20*F and below, use breathable footwear and outerwear. 20*F and above, use waterproof footwear and outerwear." Sometimes they use 10*F as the breakpoint. Whatever temperature you use, the concept is intuitively obvious. Still, I wondered, why won't other materials work as well? Why canvas?

There have been several threads on the continuum of waterproof vs breathable. There is a third leg to that stool: windproof. Canvas is highly windproof and highly breathable. Untreated canvas doesn't handle water well. Other fabrics are water resistant, windproof and breathable, but none are as windproof and as breathable as canvas. Why does that matter?

It all became clear to me when I realized what temperature differential we have between our bodies and the ambient conditions. At -15*F, there is a 100 degree difference between our skin and the air! If it's 85*F at your skin, and -15*F outside, that's 100*F difference... that's huge! Still, why does that make canvas so special?

Everyone has heard that nature abhors a vacuum. Nature also abhors a differential. When ever there is a difference in something across a boundary, there is a natural driving force to level it out. This works with water levels, salt concentrations, and many other things, including temperature differences.

Temperature differential is the driving force of heat transfer. The higher the temperature differential across an insulator, the more heat will be lost through the insulator. What makes this important in extreme cold weather is the other differential, which works hand in glove with temperature: humidity.

Inside your toasty nest, it could be 50% relative humidity or higher. Outside your hammock and all of your insulation, it could be -15*F and 30% relative humidity or much lower. That is a relative humidity differential of 20% or more. However, it is a much larger humidity differential that you would think, just looking at relative humidity.

At 50*F and 50% relative humidity, the absolute humidity is 25 grams per cubic meter, and the dew point is 26*F. Compare that to -15*F and 30% humidity, where the absolute humidity is 0.5 grams per cubic meter. Using absolute humidity, which measures the actual amount of water in the air, there are 25 grams per cubic meter inside your hammock, and only a trace of water vapor in the air outside! That is a gigantic difference.

So, what happens is the temperature and humidity differences work together to drive both heat and moisture out of your hammock, right through your insulation. The result is both heat loss and condensation. There is no way to avoid either in such extreme conditions. Heat loss can be minimized by using lots of insulation. Condensation can be minimized, too. How? By using breathable insulation with canvas outside! (You saw that coming, right?)

The canvas will keep out the cold wind, but allow the moisture through. The trick is to get most of the moisture to go right through your insulation in the vapor phase, without condensing and making ice. For that to happen, a highly breathable outer layer is required. Canvas doesn't inhibit the flow of water vapor through your insulation, so it allows the water vapor to escape into the air without much condensation.

Of course, your clothing and hammock insulation must be breathable for all this to work. For instance, if you have a vapor barrier under your hammock, that stops the moisture cold, so to speak. With luck, you won't find ice crystals there when you hang in Minnesota!

Think about what happens if you use waterproof boots in extreme cold. There is a lot of water generated by your feet when you are active. ("Over 2 cups per day!" says FourDog.) If your boots are waterproof, that water stays in. It gets into your socks and the insulation of your boots. Then, you remove your foot and go to sleep. If you don't dry out the inside of your boots, all that water will freeze. OTOH, canvas and leather mukluks are highly breathable, so the moisture goes right out into the ambient air, so that socks and liners are relatively dry when you remove your feet.

Extreme cold air will dry you out fast. That's why we have to rehydrate more than normal in those conditions. We make that attribute work to our advantage when we use breathable insulation covered with canvas. We get that cold air to pull the moisture right out of our insulation, without condensing, so that our insulation doesn't collect ice crystals, and remains in top condition to keep us warm.

Of course, there is another side to this story, and I welcome folks to explain that as well. I just wanted to explain what I have learned about breathable systems with canvas, and why it works. It has been a lot of fun making traditional anoraks, mukluks and hammock socks using canvas, and seeing them work just like they are supposed to do. I hope this helps folks understand why.

- MacEntyre

[MAD777]

Excellent presentation! 'Nuf said :)

[RAW]

So, with this information in mind, what are the best methods to keep yourself warm AND travel light a)on your person? and b)for hammocking?

I've been eyeballing the anoraks and such from Empire Canvas.
But I keep thinking about the weight. And how that stuff doesn't do double duty.

I like that my Driducks poncho is somewhat breathable and can be strung up under my hammock and underquilt for a small boost. But is it breathable enough under 20º?

And my guess is that IX would fall into the over 20º category then, right?
Or does it breathe well enough in most cases?

[Rug]

Thanks for the write-up.

[MacEntyre]

So, with this information in mind, what are the best methods to keep yourself warm AND travel light a)on your person? and b)for hammocking?
Many people this winter have commented that without a pulk, they would be hard pressed to pack all their stuff! The bulk is mostly down, though.

I wear my canvas anorak and mukluks, so the only canvas item I would pack would be a canvas sock. (I'll have one for Roan Mtn.) It's about 100% heavier and 50% bulkier than an IX Hammock Sock.


I've been eyeballing the anoraks and such from Empire Canvas. But I keep thinking about the weight. And how that stuff doesn't do double duty.
I used the anorak to cover the foot end of my hammock. What more do your waterproof boots and poncho do for double duty?


I like that my Driducks poncho is somewhat breathable and can be strung up under my hammock and underquilt for a small boost. But is it breathable enough under 20º?
I think not, or at least not breathable enough to take this approach.


And my guess is that IX would fall into the over 20º category then, right? Or does it breathe well enough in most cases?
Correct!

However, Canoeski had good results using a Baby Orca right under his hammock in MN. Thing1 and I did the same at Mt Rogers. It doesn't block all the vapor, since it's a 3/4 UQ.

FourDog used a piece of reflectix right inside his hammock, so his rig was not completely breathable. At any rate, if you do use a vapor barrier, it should be right under you or your hammock. Any further away is asking for condensation and ice crystals.

In MN, I had no vapor barrier of any kind in my SnugPod.

[MacEntyre]

Excellent presentation! 'Nuf said :)
Thank you!

Thanks for the write-up.
You are entyrely welcome!

[mbiraman]

Thanks John. I'm glad to see this being talked about more. The truth is for any activity where there is exertion so that you sweat, not talking about rain here, there has not been anything made in decades to replace the abilities of natural fibers. For walking across the street to your car or around town fine but for work/workout , no. Most of the products on the market today are made for the middle class consumer market that get out on the odd weekend. Their fashionable, neat colors with cool names. I get nostalgic for the days when so many of my friends wore Stanfield grey label underwear tops and wool pants. We would work hard and when we rested you could see the steam just pour up from our bodies. I still do this and won't win a fashion contest. Modern fabrics have their place, i have some, and its a process to figure it all out.
I think a cotton anorak could be useful for "cool" temps as well when your hiking , no rain or snow, and you stop for lunch and dawn your anorak to protect you from wind chill but still breath. JMO
bill

[RAW]

So, next question:

Where's the magic compromise for canvas weight/thickness?
Thin enough to not weigh 10#, but thick enough to block wind/trap heat.

[MacEntyre]

Thanks John.
You are entyrely welcome!


...the middle class consumer market that get out on the odd weekend.
FourDog and I talked about that... for "weekenders," which most of us are, it doesn't matter as much. But for spending days in the woods, or in a survival situation, your gear becomes critical, and breathable fibers shine in extreme cold.


Where's the magic compromise for canvas weight/thickness? Thin enough to not weigh 10#, but thick enough to block wind/trap heat.
As light as possible! You could make an anorak from tightly woven cotton bed sheets, although that's a little too light for me. It's hard to find Egyptian cotton canvas, which is a little heavier than a bedsheet, but I have come very close with a local source.

[mayday]

I returned from my second OKPIK week at the Northern Tier High Adventure Base in Ely, MN. By the way, OKPIK is Inuit for "snowy owl" - a creature that is comfortable in the cold North. Anyhow...I took my Gortex parka and Sorel boots with removable liners. Here is what I found...

Warm moisture from our bodies will move away from our skin and into our layers only until the warm moist air comes into contact with cold air. When I wore Gortex (this trip was between a low of -24 and a high of 0) the Gortex did not breathe! The pores stopped up with the frozen moisture! In fact I felt very clamy. When I switched to my canvas Anorak and the canvas mukluks instantly I found the solution to arctic cold camping!!!

The canvas enabled the moisture to escape ("breathable) and I was not clamy the rest of the week. It was amazing! The canvas pores are larger than the Gortex and therefore more breathable! If you go to Stegers Mukluks in downtown Ely, you will look at their boots (as I first did) and you will say "I thought cotton kills? How can this canvas boot keep my feet warm and dry?"

Here is the deal: The BSA classifys winter camping into three categories; 50 to 32 degrees, 32 to 15 degrees and below 15 degrees. Here in East Tennessee it rarely goes below 0. So, we wear Gortex since our snow is WET and there is a higher cahnace of rain, sleet and wet snow. In Minnesota we never saw a day above zero. The snow was DRY! It is not going to melt unless I melt it!

So, IF I stepped in slush on a lake all I had to do was put snow on my boot and the snow absorbed the water and my boot became dry! My Sorel (if wet) would not have dried for a long time.

So....LONG LIVE CANVAS FOR EXTREME COLD AND DRY SNOW!

[Carver]

Great review, Mac. When will the canvas pictures be up on mollymacpack.com? "Could not be more better."

[MedicineMan]

Its a geographical argument.
Just remember that if you want an economical and extremely lightweight method to prevent moisture from entering your downy goodness use a vapor barrier. Sac or suit
doesn't matter-your moisture won't be going through the sil-nyl (if your vapor barrier is
sil-nyl) and into your insulation. Inside your downy goodness and inside your VPL you'll be warm and damp...the only pain is in the morning when you climb out of that warm wetness and put on your hiking clothes. It can be a shock you'll never forget-damp and naked at 8F--but you'll get out of the VPL and into clothes quickly!
The same lightweight economical approach has been used for a long time on the feet with bread sacks against skin and then the socks-same principle, the plastic bag prevents moisture from entering the socks/boots.
If you live in the north country you'd def. have a lot of canvas items or even Ventille...in the south where as mentioned above below zero is rare, there is this optional approach using VPLs. It's up to each hiker/paddler/explorer of course to weigh
the humidity, the temps at hand, how much you want to carry and make your decision.

[koaloha05]

Mac, thanks for the info. Personally I find breathable & highly wind resistant outer gear to be a necessity for cold winter outdoor comfort.



...I've been eyeballing the anoraks and such from Empire Canvas.
But I keep thinking about the weight. And how that stuff doesn't do double duty...

Heavy weight may not be necessary except for durability, abrasion resistance. Have a very old & much used light "canvas" anorak. Not 100% cotton. Material is densely woven from a relatively fine thread. Very windproof and very breathable. Very soft feel. Zero waterproofing. A plus is the body moisture "wicks" to the outer surface and then freezes. Never feel wet unless temps are warm or after coming in from the cold. Key is wearing the proper base layer(s). Used from +12,000 ft in the mountains to here in midwest during the winters. Ski touring, X/C training, winter runs, snowshoeing. Just came in from a run wearing it. Bit faded & getting "thin" in some areas.

Maybe the people at ECW would consider a 3 or 6 oz weight canvas?

[MAD777]

I returned from my second OKPIK week at the Northern Tier High Adventure Base in Ely, MN.

So....LONG LIVE CANVAS FOR EXTREME COLD AND DRY SNOW!

Thank you for the collaborating evidence! Most of us don't see these conditions but as more and more forum members are surviving these trips, I'm all the more intrigued! It's great to learn from the experience of others.

[MacEntyre]

Its a geographical argument.
Au contraire. It's a temperature and humidity concern. If temps will be below 20*F, you can use breathable footwear and outerwear.

I understand the alternative to a completely breathable layered approach, but the idea of waking up warm and moist has no appeal for me! :eek:

I carry Tingley's 17" Rubber Overboots just in case there is a warmup... I would switch out the anorak for a lightweight poncho, if wet precipitation made that necessary. Otherwise, if the forecast shows no chance of temps above 25*F, I'll go with canvas.

[MacEntyre]

Great review, Mac. When will the canvas pictures be up on mollymacpack.com?
Soon! :thumbup:

[OutandBack]

Soon! :thumbup:

Jeez Mac, If everyone is wearing Mukluks and Anoraks at the next Minnesota
Winter Hang how are we going to know which one's you? :lol::lol::lol:

All kidding aside, enjoyed your info and looking forward to seeing your new goods on the website.

[oldgringo]

I really appreciate an engineer that can discuss technical topics w/o giving me a headache. Thanks for that.:)

[stairguy]

Its a . Inside your downy goodness and inside your VPL you'll be warm and damp...the only pain is in the morning when you climb out of that warm wetness and put on your hiking clothes. It can be a shock you'll never forget-damp and naked at 8F--but you'll get out of the VPL and into clothes quickly!
.

At the Minnesota Frozen Butt my sleep system included wearing my 24 oz wool pants and my Empire Canvas Works blanket shirt,both which were worn during the day, both which aloowed breathability. It was like sleeping w/a wool blanket. There was no need to wake up wet and get naked.

[MacEntyre]

Jeez Mac, If everyone is wearing Mukluks and Anoraks at the next Minnesota Winter Hang how are we going to know which one's you? :lol::lol::lol:

See my new hat below.


I really appreciate an engineer that can discuss technical topics w/o giving me a headache. Thanks for that.:)
You are entyrely welcome, Dave! I bet you know more than most about temp and humidity.


...no need to wake up wet and get naked.
...and it would have been dangerous, as well. Exposed skin was at risk!

[tjm]

http://wintertrekking.com/index.php?action=article_view&a_id=28

This link also discusses using canvas as an outer layer and backs up many of the comments made in MacEntyre's excellent post.

I appreciate the repeated clarifications that this layering strategy has a very specific application: deep cold, low humidity, hot tent and/or a camp fire.

[gunner76]

Excellent write up. Forced the old brain housing group to reread it and do some work (thinking about what you said). Makes sense and good info to know and use in the cold.

[MacEntyre]

...you'll be warm and damp...
Upon further reflection, it occurs to me that the fundamental difference in that approach is that you collect all of the moisture and then dry it out.

How do you dry everything?


This link also discusses using canvas as an outer layer...
I've read that! Great information. Having the 'engineer defect' it was necessary for me to reflect on the numbers to really appreciate the magnitude of the problem.

Us'ns in our clothing are near tropical, and right outside our clothing it's a frigid desert!


I appreciate the repeated clarifications that this layering strategy has a very specific application: deep cold, low humidity, hot tent and/or a camp fire.
Well worth repeating... it only works under extreme conditions.


Excellent write up. Forced the old brain housing group to reread it and do some work ...
Thank you!

Actually, you are likely to have a good understanding of the fundamental issue... don't you use greenhouses in winter?

[Festus Hagen]

Informative post! Makes me wonder if my choice of a 1pc "Carhart" style overalls that I wore at my first winter camping trip wasn't a stroke of unintentional mad genius (of course, I've "upgraded" to Gore-tex and nylon outer layers, d'-oh!) Is "cotton duck" the same thing as "cotton canvas"?

All that said and acknowledged, on "the night of -36" I wouldn't have sold my Sorel 1964s for $500 (rubber bottom section, leather upper), nor my MollyMac IX hammock sock for $1000 :)

[Bradley]

Funny . . . I have a 50 yr old tarp that is, as good as, the day it was 5yrs old,

weighs a tonne (That would be a ton equivilant, that = ???)

I have had it for 25yrs, and it is toooo heavy to use for any thing . . .
Took it car camping to use as a ground sheet . . .
but decided to leave it in the car . . . tooo heavy.

I have been wondering what to do with it . . . :sleep:

:eek: Bing . . . mucklucks, yea . . . I think I'll cut them up for Mucklucks.
For the whole family

Thanks guys :laugh:

[Theo]

Good to see this discussion. I've always had better luck, overall, with natural fibers than with synthetics. I tried the vapor barrier system years ago and I had to give it up. I never woke up warm and damp. I always woke up cold and wet. I don't perspire when active, I sweat like a tropical rain storm. Still wear cotton socks down to about 40* so I can get the sweat out of my boots. ( My feet even get sweaty in crocs )

[Roadtorque]

I think this helps explain my first hammocking experience. I used an old army half shelter which I believe was made from canvas which I strung between two trees and used as a hammock. It was winter in Utah and one of the coldest mornings I ever remember waking up to. The only insulation I had was the sleeping bag in the hammock and I stayed warm all night. Now that I know a lot more about hammocks I've always wondered how I was able to stay warm that night with no pad and no uq.

[MacEntyre]

Is "cotton duck" the same thing as "cotton canvas"?
Yes. Ideally, you want 300 to 400 thread count, which is lighter than 7 oz canvas.

The ~7 oz canvas you get from fabric stores is not very high quality. Every edge has to be roll hemmed, or it will fray until it falls apart. :eek:

[Knotty]

Excellent post Mac. Thanks for providing such an understandable explanation.

[Redoleary]

Great info Mac, thanks.

[MacEntyre]

Excellent post Mac. Thanks for providing such an understandable explanation.

Great info Mac, thanks.
Ya'll are entyrely welcome! Thank you for the kind words!

Pictures of mukluks, anoraks and canvas socks are up on the web site (http://www.mollymacgear.com/canvas.html)!

More pictures are coming...

- MacEntyre

[Shug]

Very thought provoking ....... good intel MacEntyre.
I am always drifting back and forth in these extreme weather worlds.
Moisture control in the deep cold .... however one does it ... is of utmost importance.
I know. I live it. Frozen nose hair ....gets ya' thinking.
Who is John?????.....:laugh:

[MacEntyre]

I am always drifting back and forth in these extreme weather worlds.
Most of us'ns be weekenders, so it may not be critical, as long as we can stay dry and safe. :thumbup:


Who is John?????.....:laugh:
Tha's me... some folks, including Bill (MBIRamen), like to use my first name. I don't mind... My family always called me "Mac" or something unprintable. You can walk up to me and say, "Hey John!" and I probably won't think you're talking to me! :rolleyes:

My brother is Jim. Our Florida cousins are all female, and they like to use one name to talk about both of us: "Jimmy-Mac!" (If'n they call him "Jimmy" now, in an exaggerated southern drawl, he responds with something worthy of a Brooklyn native, but unprintable!)

[MedicineMan]

'Upon further reflection, it occurs to me that the fundamental difference in that approach is that you collect all of the moisture and then dry it out.
How do you dry everything?'

OK, my experience using vapor barriers in only in the east--the normally high humidity east; but in the deep cold where you'd use a VPL most of the time the humidity is low-even in the east....just overheard a coworker last week complaining about her cracking skin on her fingers....My VPL barrier of choice is the extremely long pack liner out of sil-nyl, big enough for you to get into ~and you get into it naked~.....in the morning that is the only thing to dry out but in reality you have your clothes lying in wait. In the 3 (only 3 times) times I've used it your skin is dry even before you get the clothes on; also at the temps you'd use this you turn the VPL sack inside out and in just moments it has frozen and simply shakes off....I think that insensitive sweat layer is very thin, it meshes with my belief that when a barrier is applied directly to the skin the body will greatly decrease its sweat output (another positive in saving water). This VPL bag is three tools in one, total body VPL, pack liner, and emergency bivy....the clincher is the weight, at 6oz and 3 functions it's my choice at preventing moisture from getting into the downy goodness.

One more comment about 'drying it out'; you'd think there would be a pint of water pooled in this VPL bag but it doesn't happen. The interior surface of the whole sack is moist--maybe if you collected it all you'd measure 1/2 cup but I've never measured it...again it goes to the suppression of sweat production when the skin is against an impermeable barrier.

I think those who use VPL suits (Wisenber please chime in here) on expeditions maybe never take them off? -or rarely do; so they climb out of the bag and pull on the down pants or maybe they slept in them too depending on how cold.

We read how Wisenber greatly increased his temp range with the VPL suit and the suits are very light compared to more and heavier quilts. So there can be a weight advantage via VPLs. But I can see how many/most would feel clammy, its a warm clammy but still sauna like.

Now about those gradients. If you are in a VPL suit or sack and the relative humidity is very very low outside then the/any moisture in your down layers will gravitate outward...so in a sense using the VPL is an effort to dry your down :)

[MacEntyre]

I can't imagine getting naked in temps below zero! :scared:

What about your footwear and clothing, MMan? Do you use vapor barriers in your boots and base layer?

[mbiraman]

Most of us'ns be weekenders, so it may not be critical, as long as we can stay dry and safe. :thumbup:


Tha's me... some folks, including Bill (MBIRamen), like to use my first name. I don't mind... My family always called me "Mac" or something unprintable. You can walk up to me and say, "Hey John!" and I probably won't think you're talking to me! :rolleyes:

My brother is Jim. Our Florida cousins are all female, and they like to use one name to talk about both of us: "Jimmy-Mac!" (If'n they call him "Jimmy" now, in an exaggerated southern drawl, he responds with something worthy of a Brooklyn native, but unprintable!)

I always called you Mac until recently when i saw your name on molly mac was John . I always felt calling you Mac was being a little curt so when i saw john i switched,,,which do you prefer??

bill

[MedicineMan]

Well you're not standing in zero temps to get the clothes on....You'll be inside a tarp which makes it warmer, and/or you can change while still being in your MacIX HammockSock which makes it warmer still; and that thing Shug breathes into....like a shamwow towel, you can unhook it from the ridgeline and use it to whipe your chest while still inside the VPL sack and then pull on your dry hike top, then repeat from the chest down as you get out of the sack or the VPL top and bottom.
So best guess here, if it is zero outside the tarp maybe 8F inside, and maybe 15F inside the HammockSock-the big plus is no wind is hitting you.

Do I? very very rarely. Remember geographical...just doesn't get to these temps often enough here in my neck of the woods coupled with how long I will typically be out. And how long do you plan to be out is the other big question. When the original successful arctic team went out they knew it was months but even if it is a week you'd better plan on serious moisture management. If I remember right the original successful team used native clothing (like skin mukluks/anoraks/etc...the unsuccessful team relied on modern marvels of the day and died)! For the typical 1-2 nigh foray it is not as critical to me. That said I think most should carry bread sacks-they weight nill on the feet in the boot or in the socks at night. If you wear bread sacks on the feet at night inside your socks you will wake up to completely dry socks.

Hey--just a hillbilly's opinion. If I were the other readers of this thread I'd listen to the engineers :)

[MacEntyre]

I always felt calling you Mac was being a little curt so when i saw john i switched,,,which do you prefer??
I have no preference. My mother-in-law, may she her wonderful old soul rest in peace, always thought I should use my entyre middle name, "MacEntyre." It rolled off her tongue in a most appealing way.


For the typical 1-2 nigh foray it is not as critical to me.
Nor to any of us... we are all weekenders, with rare exceptions. By the time ice accumulates in our insulation so's we'd notice, we are almost at the car!

[MacEntyre]

Jeez Mac, If everyone is wearing Mukluks and Anoraks at the next Minnesota Winter Hang how are we going to know which one's you? :lol::lol::lol:
OTOH, I could go incognito...

[Carver]

According to an article in a 1987 issue of Backpacker magazine, polar explorer Will Steger's synthetic sleeping bag had, "gained as much as 50 pounds of condensed frozen moisture." It would be interesting to find out what changes were made in later expeditions. I suppose they have to go with whatever gear their sponsors provide.

[Shug]

When I did my -26º trip .... my Thru-Hiker top made of Climashield and Momentum froze solid. Stiff. As a board.
Good shirt in cold above 0º .... but does not go in the sub 0ºs anymore.
I learned something.
Shug

[stairguy]

According to an article in a 1987 issue of Backpacker magazine, polar explorer Will Steger's synthetic sleeping bag had, "gained as much as 50 pounds of condensed frozen moisture." It would be interesting to find out what changes were made in later expeditions. I suppose they have to go with whatever gear their sponsors provide.

I believe if he had been using a down bag he would have been in big trouble.

[MedicineMan]

The true north arctic is a funny place, a very wet place.
I looked at these readings, current as of 0200 this morning:
TUKTOYAKTUK, NWT, CANADA

Fahrenheit). Air pressure was 1,015 hPa (29.97 inHg). Relative humidity was 58.5%. There were a few clouds at a height of 2743 meters (9000 feet). The visibility was 24.1 kilometers (15.0 miles).

IGLOOLIK, NUNAVUT, CANADA

Weather report as of 583 minutes ago (21:00 UTC):
Fahrenheit). Air pressure was 1,006 hPa (29.72 inHg). Relative humidity was 2,985.6%. There were a few clouds at a height of 762 meters (2500 feet) and a few clouds at a height of 1676 meters (5500 feet). The visibility was 24.1 kilometers (15.0 miles).

RESOLUTE, NUNAVUT, CANADA

Weather report as of 43 minutes ago (06:00 UTC):
Resolute, Canada. The temperature was -27 degrees Celsius (-17 degrees Fahrenheit). Air pressure was 1,017 hPa (30.02 inHg). Relative humidity was 68.5%. There were broken clouds at a height of 975 meters (3200 feet).

POND INLET, NUNAVUT, CANADA

Weather report as of 43 minutes ago (06:00 UTC):
The wind was calm in Pond Inlet, Canada. The temperature was -35 degrees Celsius (-31 degrees Fahrenheit). Air pressure was 1,007 hPa (29.75 inHg). Relative humidity was 66.5%. The sky was clear. The visibility was 14.5 kilometers (9.0 miles).

BARROW, ALASKA, USA

Weather report as of 23 minutes ago (06:20 UTC):
The wind was blowing at a speed of 2.1 meters per second (4.6 miles per hour) from North in Barrow, Alaska. The temperature was -2 degrees Celsius (28 degrees Fahrenheit). Air pressure was 1,006 hPa (29.70 inHg). Relative humidity was 100.0%. There were a few clouds at a height of 457 meters (1500 feet), scattered clouds at a height of 853 meters (2800 feet) and broken clouds at a height of 1372 meters (4500 feet). The visibility was 16.1 kilometers (10.0 miles).

THULE, GREENLAND

Weather report as of 48 minutes ago (05:55 UTC):
The wind was blowing at a speed of 4.1 meters per second (9.2 miles per hour) from East in Thule, Greenland. The temperature was -28 degrees Celsius (-18 degrees Fahrenheit). Air pressure was 1,002 hPa (29.58 inHg). Relative humidity was 68.3%. The sky was clear. The visibility was >11.3 kilometers (>7 miles).

Can't wait for the engineers to tackle this one.
A hillbilly would use 2 vapor barriers...one your in and one the sleeping bag is in. Down or synthetic would act as a giant sponge sucking the moisture out of the air at those humidities, the outer barrier would slow this, the inner would slow your body moisture from getting sucked into the insulation.

Ironically the Antarctic is one of the driest places on earth with an average humidity of 0.03% Might as well call it a dessert.

[oldgringo]

OTOH, I could go incognito...

That is disturbing. Small children will be scarred. And scared.;)

[MacEntyre]

Ironically the Antarctic is one of the driest places on earth with an average humidity of 0.03% Might as well call it a dessert.
The Arctic is an ocean, and the Antarctic is a continent. Of course. an ocean will be more humid. But the Arctic is not as wet as you think. Relative humidity is, well, relative. It's relative to the total amount of water vapor that the air can hold at the current temperature. At those low temps, the air will not hold much water vapor at all, so your high relative humidity readings for the Arctic are still dry as a desert. Look up the absolute humidity for those temperatures and compare them to higher temps, and you will see what I mean. (Or, you can reread the original post in this thread.)

OldGringo, fear not for the children... I will have a hood on! (Besides, I made sure the heads and feet were tucked inside...)

Stairguy, I wonder how a buffalo robe would do?

Shug, what do you wear now in those temps?

[Carver]

In the Lake States in the horse and buggy days, the long coat of choice was bear skin. The sleeping mat in AK was a very heavy caribou skin with just a few bot holes.

[TZBrown]

I think those who use VPL suits (Wisenber please chime in here) on expeditions maybe never take them off? -or rarely do; so they climb out of the bag and pull on the down pants or maybe they slept in them too depending on how cold.

We read how Wisenber greatly increased his temp range with the VPL suit and the suits are very light compared to more and heavier quilts. So there can be a weight advantage via VPLs. But I can see how many/most would feel clammy, its a warm clammy but still sauna like.

Now about those gradients. If you are in a VPL suit or sack and the relative humidity is very very low outside then the/any moisture in your down layers will gravitate outward...so in a sense using the VPL is an effort to dry your down :)

VBL are very usefull if you have the ability to not over exert during working activities. A VBL can easily cause heat exhaustion if used incorrectly.


According to an article in a 1987 issue of Backpacker magazine, polar explorer Will Steger's synthetic sleeping bag had, "gained as much as 50 pounds of condensed frozen moisture." It would be interesting to find out what changes were made in later expeditions. I suppose they have to go with whatever gear their sponsors provide.

Steger did eventually use VBL in his sleep systems during later outings to reduce ice buildup in the sleep systems

I did not get to read this thread before Monday. Lots of great information here.

Mac your portrait photos are just to much. :lol::lol: Love the new hat

TZ

[MacEntyre]

:lol::lol: Love the new hat
Vintage furs are available at severe discounts these days... :cool:
I'm redeploying rabbit fur coats for anorak ruffs. :eek:
But what can you do with kit vixen? :confused:

Re: VBLs... It occurrs to me that Canoeski's and Knotty's approach, putting an IX UQ right under the hammock, is a good solutionm which works well with a breathable system. IX is barely breathable, and it adds 15 to 20*F to your UQ rating. It will prevent moisture from going into your UQ while it makes you warmer. If it collects a lot of moisture, you can remove it while you dry it.

Certainly, if you use an IX Hammock Sock in extreme cold weather, you must have another VBL, such as an IX UQ, right under the hammock.

[Bradley]

In the Lake States in the horse and buggy days,
the long coat of choice was bear skin..
I designed and built (DIY) what I have called a TLC
Texas Long Coat, ca.1990
I used double scraped Elk Hide.
The hide as it was made was intended to be swade side out as it was, near perfect,
but I choose smooth side out as it was distressed,
but not the on purpose type of distressed, more natural from the tanning process
Its a fair thin, and while walking on a calm day,
the bottom fronts, flow like a flag, some what, out towards the sides.
The edge's of the collar and sleeve’s are double braided,
It is double breasted, and in warm weather folds back each to it's own side and buttons.
The buttons are an inch in Di. and are brass, with a putter insert.
The bottom edge is a jagged, rough cut from the time it was skinned out.
Down near the bottom, on each side, are concho's,
2 on one side and three on the other,
each concho has a double leather lace tong hangin about 8" long
on each tong is little brass balls, strategically placed so as to hit the concho below,
giving a just audible clack, clack, clack, as I walk.

PS. The weapon in the photo is a levered Winchester 30-30, not my preference,
as I much more enjoy a levered Marlin 30-30 side load, side eject.
http://www.1stchoicehorseshoeing.com/images/shoe/TLC-Front1222.jpg http://www.1stchoicehorseshoeing.com/images/shoe/TLC-front222.jpg http://www.1stchoicehorseshoeing.com/images/shoe/TLC-back222.jpg

[Youngblood]

I hesitated to comment on this as I don't have any significant experience with this but I believe that there is something messing in this discussion of what works and when, where, and why. And I'm thinking that is sublimation, or specifically when ice converts directly to a vapor without first turning into a liquid. Here is a link I found when I Googled:

http://ga.water.usgs.gov/edu/watercyclesublimation.html

And here is part of that:

Sublimation occurs more readily when certain weather conditions are present, such as low relative humidity and dry winds. Sublimation also occurs more at higher altitudes, where the air pressure is less than at lower altitudes. Energy, such as strong sunlight, is also needed. If I was to pick one place on Earth where sublimation happens a lot, I might choose the south face of Mt. Everest. Low temperatures, strong winds, intense sunlight, very low air pressure—just the recipe for sublimation to occur.

Dave Thurlow of the Mount Washington Observatory offers a good explanation of sublimation in The Weather Notebook:

"There's more than one way for Mother Nature to get rid of a fresh blanket of snow. The most common way, of course, is by melting-which gives everyone the pleasure of trudging through slush, mud, and water. But in the western U.S., there's a wind called the Chinook, or "snow eater," that vaporizes snow before it even has a chance to melt."

"Chinook winds are westerlies from the Pacific whose moisture gets wrung out as it passes over the Rocky Mountains. Once these winds come down from the mountains onto the high plains, they can be quite mild and extremely dry-as warm as 60 or 70 degrees Fahrenheit -- over 15 Celsius -- with a relative humidity of 10% or less. The air is so dry that when it hits a snowpack, the frozen water evaporates, going directly from the ice to vapor and bypassing the liquid phase entirely. This is called sublimation, and it's a common way for snow to disappear in the arid West."

[Bradley]

Water
Snow (http://www.hammockforums.net/wiki/Snow) and ice (http://www.hammockforums.net/wiki/Ice) sublimate, although more slowly, below the melting point (http://www.hammockforums.net/wiki/Melting_point) temperature. This allows wet cloth to be hung outdoors in freezing weather and retrieved later in a dry state. In freeze-drying (http://www.hammockforums.net/wiki/Freeze-drying) the material to be dehydrated is frozen and its water is allowed to sublimate under reduced pressure or vacuum. The loss of snow from a snowfield (http://www.hammockforums.net/wiki/Snowfield) during a cold spell is often caused by sunshine acting directly on the outer layers of the snow. Ablation (http://www.hammockforums.net/wiki/Ablation) is a process which includes sublimation and erosive wear of glacier ice (http://www.hammockforums.net/wiki/Glacier_ice).

.................................................. .................................................. ..................

[MacEntyre]

Bradley, I want that coat to go with my straight stock Marlin 336 in 30-30!

Youngblood, good point about sublimation. That is how ice magically disappears from things such as Shug's bib, and my wild rag, and the outside of the top blanket, when they are covered with frozen breath vapor. However, it is much more difficult for sublimation to rid your down UQ of frozen moisture when it is not on the surface. Sublimation requires a bit of air flow, else the air becomes saturated. The buildup of ice inside the UQ, that won't go away, is what's bad.

[oldgringo]

Sublimation that you see every day: shrinking ice cubes in your freezer.

[Youngblood]

Bradley, I want that coat to go with my straight stock Marlin 336 in 30-30!

Youngblood, good point about sublimation. That is how ice magically disappears from things such as Shug's bib, and my wild rag, and the outside of the top blanket, when they are covered with frozen breath vapor. However, it is much more difficult for sublimation to rid your down UQ of frozen moisture when it is not on the surface. Sublimation requires a bit of air flow, else the air becomes saturated. The buildup of ice inside the UQ, that won't go away, is what's bad.

My point is that ice will not magically disappear from things such as Shug's bib unless the conditions for sublimation exist and they do not exist just because it is cold.

Case in point for us older folks that were around when we had to occasionally take everything out of the freezer section of refrigerators and manually de-ice them because they continually froze the moisture in the air as we opened the freezer and allowed moist air to enter which allowed that moisture to freeze and build up into ever increasing ice packs. Now days the freezer section has what is called automatic defrosting, but when that was new, that was optional and at a cost.

With automatic defrosting (which is dry air circulating through the freezer) the ice will actually disappear over time from ice trays instead of building up. The build up of ice versus the disappearance of ice occurs at the same temperatures. The difference is the circulation of dry air and not how cold the air is.

[MedicineMan]

OK I like the jacket too EXCEPT for the open butt (nicer way to put that?).
My lever of choice-Rossi Puma in .44mag, why? All I could get in stainless.
Why stainless-because I live in a rain forest :)

[MacEntyre]

My point is ...
...well made! Thanks!


Sublimation that you see every day: shrinking ice cubes in your freezer.
Now you know why... :mellow:

OK I like the jacket too EXCEPT for the open butt ...
It's a Duster, for horseback.

I just saw a white cotton duster at a local Western store. Me like!

[Festus Hagen]

Certainly, if you use an IX Hammock Sock in extreme cold weather, you must have another VBL, such as an IX UQ, right under the hammock.

My double layer DD hammock is advertised as "waterproof" which is supposed to be a plus in case you have to use it as a bivy tent. I wonder if this qualifies it as a VPL as well? I'm sure the layer of 3/8" CCF pad I had between layers didn't hurt matters either.

[MacEntyre]

I wonder if this qualifies it as a VPL as well?
Yes! :thumbup:

I like to keep the vapor barrier layer in reserve, but if your hammock is your vapor barrier, you will always be using a vapor barrier! Just keep an eye out for condensation, and be prepared to ventilate if it becomes excessive.

On a trip into the Gorge last fall, I forgot my top blanket. Hickery loaned me his reserve space blanket. The low was about 40*F that night. The space blanket became soaked with condensation quickly, but I just turned it over. That happened several times during the night. I was fine!

[Roadrunnr72]

So would it be wise to make a down UQ with canvas on the outside and nylon on the inner? It would be windproof and let the moisture out.

[MacEntyre]

So would it be wise to make a down UQ with canvas on the outside and nylon on the inner? It would be windproof and let the moisture out.
I asked FourDog why I shouldn't put a thin wool liner in my anorak, and he said, "You eliminate the advantage of layering." Same thing with your UQ. You want to be able to remove the canvas layer when it's not so cold out.

Of course, you could have a dedicated winter UQ. I'd rather have a canvas sock, which I could use with any UQ.

[Roadrunnr72]

Nice thinking. Your right, that would be better.